Implantable medical devices are used to treat a variety of diseases, and their use is increasing. Many implantable medical devices employ medical leads to deliver electrical therapy to a patient or to monitory patient parameters. The leads are connected to the active device, which is typically implanted subcutaneously in the patient, and extend from the implanted device to a target location of the patient. The leads typically have a length greater than needed to extend from the device to the target location to ensure that the lead will be of sufficient length for almost all patients and almost all circumstances. Typically the lead is tunneled from the subcutaneous pocket to the target location. Excess lead length is then wrapped or coiled and placed in the subcutaneous pocket. The manner in which the lead is wrapped or coiled can vary from implanting surgeon to implanting surgeon and can affect, among other things, flex life performance of the lead, the extent of lead abrasion, and the size of the implant pocket and corresponding incision.
Problems with lead abrasion may be exacerbated with rechargeable active implantable medical devices and excess coiled lead. If the coiled excess lead or a portion of the lead crosses the face of the device between the device and the patient's skin, the likelihood of lead abrasion may increase. Because the primary recharge coil of an external recharge head is placed adjacent the patient's skin in a location over the implanted device, the lead may be impacted between the recharge head and the implanted device causing abrasion of the lead.
In many rechargeable implantable devices, the secondary coil or the recharge coil of the implantable device is not centered on the geometric center of the device, which could lead to inefficient recharge. When the patient recharges the implantable device, the patient palpates their skin to identify the location of the implanted device. The recharge head is then located over the skin in the location identified by the patient. If the patient centers the recharge head the geometric center of the implanted device and the geometric center of the recharge device is not the center of the recharge device, coupling between the primary and secondary coils may not be optimized and thus may be inefficient.